to start off, bondo is not an adhesive. it will not hold things together. you want to fill a large area with something like epoxy or fiberglass, and then bondo over the tiny grooves that are left. plexiglass is one of the most widely used supplies in the modding community. you can get it in all sizes, and colors. i can link you to some good vendors if you are interested. finally, if you go with acrylic you can use a type of acrylic bonding agent. it actually melts the two pieces together. link.